There are three main technologies: Evaporative Cooling, which uses water-absorbent fabrics and is cost-effective for low-humidity environments; Phase Change Material (PCM), which uses inserts that maintain a constant temperature (e.g., 14°C/57°F) for several hours and works in high humidity; and Vortex/Compressed Air systems, which are ideal for stationary industrial workers near air lines. For B2B buyers, PCM vests are currently the most sought-after due to their stability and lack of condensation.